This is a long term study of characteristics of people who have been bullied.
They compare the effects of bullying to PTSD.
It is an interesting study, but I think their conclusions are mostly bullshit. People react to this differently, and much of how you react to bullying depends on your parents. Unless you decided to become a victim (supported by the stupidity of parents) .
Better solution? Teach your kids Muy Thai and BJJ.